Py3k compat for clang-format Sublime Text extension.

Sublime Text 2 uses Python 2.6
Sublime Text 3 uses Python 3.3

The `print` function has been available as a __future__ import since
2.6, so use it.

Patch by Johan Engelen!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194287 91177308-0d34-0410-b5e6-96231b3b80d8